The present invention is with respect to a blower unit which may be used in air-conditioning plant and for other purposes. Such a blower unit may, for example, have a outer housing with a first inlet or aspiration connection forming part of an aspiration duct for a primary volume flow, and with a second aspiration connection forming part of an aspiration duct for a secondary volume flow, and with an outlet or pressure connection joined up with the return air duct of the primary circuit and a pressure or outlet connection forming part of the return air duct of the secondary circuit. Such a blower unit may furthermore have two motor-powered impellers which are supported by bearings and whose outlet connection has an distributor unit designed for adjustment between different positions and with whose help the incoming volume flows at the outlet side of the blower impeller may be switched, as may be desired, for distribution between the two pressure connections.
Such systems are known in the art and have been designed with the purpose of making for simpler installation of heating and air-conditioning plant and the like in a building, and furthermore for cutting down the amount of driving power needed. In such known units, however, the impellers have to be able to undergo adjustment axially in relation to the housing, for which reason a complex system for moving the impeller is needed. Furthermore, in this case, every adjustment gives a new ratio between the impeller breadth and the breadth of the housing, this having an effect on the efficiency characteristic so that great changes therein will be likely. Furthermore, in the case of this known plant, the use of drum-like impellers is not possible for aerodynamic reasons because, as will be clear, a drum-like impeller has to be used with a fixed design of housing if good aerodynamic properties are to be produced. Furthermore, in the case of such known plant, fans with aspiration openings on two sides are not possible.